Thermostatically controlled heating system for tobacco barns and the like



THERMOSTATICALLY CONTROLLED HEATING SYSTEM FOR TOBACCO BARNS AND THE LIKE Filed May 6, 1946 April 26, 1949- G. w; HARDING 2,468,665

f 9 1 w'" E 9 A2 L l 9 v 5 gwumq bwb o fiWHardz'ny viii" *7 V E WWI/24AM Patented Apr. 26, 1949 THE LIKE THERMosTATIoALLy' commune-HEAT- mo SYSTEM or: T

BAQCO BARNS AND George Wiley Harding, Lynmmrg; Va.', 'assignor burg, Va.

to Automatic Draft andSt'o e 00., Inc., Lynch- Application May 6, 194,61

2 Claims. (creat -2)- "This invention relates to thermostatically con trolled heating systems for barns and the like, "and'pa'rticularly tobacco barns employing the hue cure method. 1" "It is common practice in tobacco barns to have a"furnace"on' the outside of the structure con- "ncted'to fiues extending through the barn so as to'heat the'structure during the curing season.

'The'tobacco is placed on racks and spaced so -air can circulate through the tobacco, but unle'ss"'a;n"even temperature ismaintain'ed imperfectly cured tobacco results. Wood as 'a'fuel is heretofore "has been "objectionable in that it is'very difficult to maintain the fire without frequent refueling and resulting differential intemperature. Where wood is the fuel'nograte is used, the air being drawn by'the fiues through the wood.

'"In my investigation I have found that the ta'ined, buta fairly high temperature.

heatingum't using wood must be airtight so that the combustion will be controlled through the inletf'ln the curing of tobacco it is essential that" not only an even temperature be main- Where the temperature in the draft is manually operated, it is virtually impossible to maintain an even temperature, and this is aggravated by the unnecessary combustion of fuel due to the draft being left open beyond the required period.

I have further found that it is highly desirable to have preheated air slowly fed to the fuel.

.By having an airtight combustion chamber, a

downdraft pipe entering the combustion chamber with a thermostatically controlled damper in the downdraft pipe, the thermostat responsive to the needs of the barn, I obtain highly successful results.

....Of. necessity, the thermostat cannot be expensive and is devoid of the fine adjustment presentin' an expensive instrument, The use of the downdraftpipe .serves as a reservoir of preheated air under operating conditions, which slowly feeds air into the combustion chamber, givingithe fire every chance to absorb the. air or oxygen, thus bringing the wood charinto a glow or. flame, and at the same time retaining the heated air within the combustion chamber so as to permit the extraction of maximum heat units from the fuel before passing into the fines.

'. The downdraft pipe might be compared to a shockabsorber in itsaction. The hot air in the downdraft has a tendency to rise, but upon the "opening of the damper in the downdraft stack, a

-draftciscreated at the chimney serving to draw the air inrthe downdraft stack into the com-' 'in the;

thei 667,

oustion chamber. It must, however, overcome the tendency of the heated air to'rise, and thus there isno rush of air which might be detrignerit'alto'-"combustion' at a low State, the preheatedair being "fed slowly into the: combustion chamber against the fuel. Should the thermostat open the damper too wide, the reservoir 'of'air downdraft stack compensatesthi's factor 'by haVihg' available an accumulated supply of stoied air which answers the'needs ofthe stove "without a sudden inrush' of air which might be detrimental at a low stage of co'mbust'ionp' It'is *"e's's entiallithat such aheating unit operateht a thermostat.

low'temperature and maintaincombustion'; run under this condition is really Warm charcoal or wood char. At the low combustion temperatures, the downdraft stack or column of preheated air contributes most to'the effective operation of the The air in the downdraft stack is heated and tends to move upwardly and the effective chimneyis relatively short since the draft is caused by the ascension" of warm air'. The effective height of any chimney is the height to which a solid column of warm air extends ;*hence sarily very slow It is little more than adrift 'during'the early stage of combustion. The slow diffusion of warm air over the warm charcoal, creates a slow air current conducting heatof oxidation to adjacent charcoal. The ideal condition for bringing up a fire from sub-incandescent temperature is for the air current to incre'a'seby amountof charcoal heatf infinitesimals in step with temperature rise and Thus the preheated -columnof' air definitely affects thebperationof the t h ermostat so that the feeding of the air onto the charcoal 'foroperation of the'damper'is graduated and refined far'beyond the normal opera- -tion of the thermostat on the valve or damper'located in conjunction with an opening at the bottom of the heating unit without such a 'downdraft stack. V r

thermostat operating a fiap Valve-not attached -to'- a'- downdraft stack would not have the compensating factor of rising air with resulting slow feedor driftinto the combustion chamber.

Atendency-for the air to rise in the flue or' exit :chimney isunimpeded. The velocity- 0f air moving over the warm charcoal will be increased the closer the air inlet is to the charcoal. If the air is diffused slowly to the warm charcoal, the temperature would climb because infinitesimal heat units would be subtracted from the charcoal, whereas if it is blown directly across the warm charcoal it would probably be cooled faster than oxidation could occur.

In a coal burning stove there is a grate on which ashes accumulate, and unless removed from it form an insulating layer on which rests closely nested coal. Below the grate bars is an air chamber in the form of an ash pit. Air usually enters through the ash door, and in order to reach the fire is drawn through the grate bars, ashes and fuel. This requires a strong draft, and the placing of a downdraft on the outside of the heater entering the ash pit will only serve to further slow down and impede the air flow, so that an entirely different problem is presented where wood is the fuel.

The principal object of my invention is to provide an airtight wood burning heating unit for tobacco barns and the like having a downdraft thermostatically controlled so located and adjusted as to result in the most efficient curing of tobacco.

Another object is to provide an attachment for flue equipped tobacco barns designed for burning wood comprising a downdraft having a temperature thermostatically controlled from within the barn and adjacent to the tobacco.

Other objects will be disclosed in the specification and claims forming a part of this application.

In the drawings:

Figure 1 is a fragmentary vertical section of the heating unit in elevation;

Figure 2 is a fragmentary front elevation of the heating unit;

Figure 3 is an enlarged detail of the downdraft and thermostat connecting mechanism; and

Figure 4 is a bottom plan view of the U-shaped member connecting the counter-balance and thermostat.

Figure 5 is a horizontal section through a tobacco barn illustrating conventional duct arrangement.

Referring to the drawings, in which similar parts are designated by like numerals:

Numeral 5 designates an airtight brick oven or heating unit which could be of any airtight construction extending from the outside into the structure to be heated, and having a fuel door 6 with a downdraft stack I extending from outside of the building into the combustion chamber 8. Extending from the rear of the heating unit 5 are a plurality of fines 9 which extend around the walls of the barn and, if desired, through the tobacco, coming together in a single flue II].

Inside the downdraft stack I is a pivotal damper I I connected to an arm I2 exterior of the stack, which in turn is connected by a chain I3 to a bell crank I4 pivoted to a support I5 and having a counterweight I6. A U-shaped channel member I7, shown in detail in Figure 4, having a plurality of adjustment holes I8 is connected by a pin I9 to a projecting toe forming a part of the lever It. A wire or rod 2| is Welded or otherwise secured to the U-shaped channel member I1 and is connected at its other end to a bi-metal thermostat 22. A support 23 extends inside of the barn or other structure having a platform 24 on which the fulcrum support I5 rests and an arm 25 extending from the support 23 having the bi-metal thermostat 22' at its outer end, the arm 25 being braced by wires 26 with turn-buckles 21 to adjust the wires. The arm 25 extends into the structure a sufficient distance and at a height to maintain the barn at a proper temperature and make the thermostat responsive to the desired temperature.

I have found that location of the thermostat approximately six feet from the floor gives the best results. A thermostatic bi-metal dial thermometer 28, with the thermometer on the. inside of the building and the dial on the outside adjacent the heating unit, serves to make available to the operator the temperature within the structure. A cap 29 is positioned over the downdraft stack, and a manually operated damper 30 is placed near the outer end of the down stack I to supplement the thermostat when desired. Tiers of tobacco 3| are arranged throughout the barn in the usual manner.

As illustrated, the thermostat control downdraft stack, damper, support, thermostat, and bell crank lever with connecting mechanism can be installed as a unit where the barn is already equipped with the heating unit and flues, or it can take the form of a complete heating unit, including the airtight heating unit and flues added to accommodate the size of the building. Obviously the size of the heating unit will depend upon the cubic contents of the building to be heated and its heating capacity will increase in proportion to the size of the structure.

As actually used, the damper II will be normally open and the responsiveness of the thermostat 22 adjusted through the holes I8 in the U-shaped member I! by placing the pin I 9 in the desired opening, thus controlling the movement of bell crank I I. The counterweight I6 will serve to offset the weight of the arm I4, the chain I3 and the damper II, 0 that although the damper will be normally open, very little effort is required to close it. The expansion of the bi-metal thermostat 22 will serve to advance the wire 2|, moving the toe 20 forward, lowering the arm I 4, and in turn the arm I2, resulting in the closing of the damper I I. Upon the interior of the barn coolingofi, the bi-metal thermostat 22 will contract, pulling on the wire 2| and through the various linkages serve to open the damper I I. The accumulated warm air in the downstack 1 serves to compensate for any inefficiency of the thermostat and results in an even heat being diffused through the barn, and a constantly maintained damper which is essential to properly cured tobacco. By inefficiency of the thermostat is meant course or sudden opening of the damper valve which attends the use of a cheap thermostat as contrasted with very gradual opening of the damper valve when controlled by a more expensive thermostat. Even though the damper valve may open wide and suddenly, there will be no sudden rush of air into the combustion chamber, due to the counterbalancing elfect of the column of warm air in the down draft stack on the head of heated combustionv products in the discharge flue. The wood fuel is placed in the heating unit through the fuel door 5, the fire box 8 being big enough to receive large pieces of wood. The automatic regulation of the damper maintaining the temperature at a constant level in the building, along with the downstack operation, serves to conserve fuel and make a most efficient and economical operation. The ducts 9 convey the heat directly from the fire box throughout the barn converging into a single discharge flue, thus conveying the heat through the structure providing the maximum utilization of B. t. u.s, portions of said ducts anterior to said discharge flue extending substantially horizontally.

Under this arrangement, maximum heat efficiency is obtained. The downdraft stack on the exterior of the structure and the ducts within the building may be likened to counterbalancers. As the warm air in the duct increases it will overcome the tendency of the warm air in the downdraft stack to rise and will draw it into the combustion chamber with increasing velocity until the desired temperature is reached, thus operating the thermostat, and in turn the damper in the downdraft stack. Under this arrangement, the smoke will ultimately find its way out through the flue but most of the B. t. u.s will be expended within the structure. As the fire dies down, the warm air in the downdraft stack will build up and that in he ducts decrease. Upon the opening of the damper, due to thermostatic action, the preheated air in the downdraft stack will gradually flow into the combustion chamber, and as the fire builds up, the warm air in the ducts will increase, increasing the rate of flow from the downdraft stack which is desirable after the low temperature phase has passed. Instead of a fluctuating heat which burns fiercely at one phase overheating the structure and quickly dying down, you have a short cycle of combustion with the damper open and a long off-cycle resulting in economy and even heat. The downdraft stack with the damper thermostatically controlled positioned on the outside of the structure at one end and the combustion chamber with the ducts extending from the other end, finally terminating in the fiue, contributes largely to these results.

Various modifications in the construction and arrangement of parts will readily suggest themselves to those skilled in the art, but within the 4.

scope of the present invention as claimed.

What I claim is:

1. A heating system for tobacco barns comprising an enclosure to be heated, a wood burning heater including a combustion chamber having a down draft stack at its forward end outside said enclosure, and a combustion products duct extending from its rear end Within said enclosure, said duct terminating in an up draft flue discharging outside said enclosure at a height above said down draft stack, the major portion of said duct between said heater and up draft flue being substantially horizontal and in heat exhange relation to the air within said enclosure, a damper in the upper part of said down draft stack, a thermostat mounted within said enclosure at a remote point from the walls thereof, and operat ing connections from said thermostat to said damper.

2. A heatin system for tobacco barns comprisin an enclosure to be heated, a wood burning heater including a combustion chamber having a down draft stack at its forward end outside said enclosure and a combustion products duct extending from its rear end within said enclosure, said duct terminating in an up draft fiue discharging outside said enclosure at a height above said down draft stack, the major portion of said duct between said heater and up draft flue being substantially horizontal and in heat exchange relation to the air within said enclosure, a damper in the upper part of said down draft stack, a thermostat positioned within said enclosure, a support for said thermostat, an arm extending from said support to a point remote from the walls of said enclosure, said thermostat ,1- being positioned at the end of said arm, a bell crank carried by said support, adjustable means connecting said bell crank and thermostat, means connected to said bell crank and said damper for operating said damper responsive to the thermostat.

GEORGE WILEY HARDING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,585,662 Gardner May 25, 1926 1,786,931 Ashley Dec. 30, 1930 2,020,295 Boname Nov. 12, 1935 2,265,587 Waddell Dec. 9, 1941 

